Method of preparing alkyl sulfonyl chloride

ABSTRACT

An alkyl sulfonyl chloride is prepared continuously in high yield by reacting an alkyl mercaptan or dialkyl disulfide having one to 20 carbon atoms in the alkyl group with chlorine in a medium comprising aqueous concentrated HCl solution, in a reaction zone free of mechanical agitation means, at such feed rates that the reaction creates a turbulent condition in the reaction zone, and passing the medium into a contiguous product separation zone wherein the alkyl sulfonyl chloride is separated and withdrawn from the aqueous medium.

United States Patent Inventor Roland Maurice Guertin Rockwood, Mich.

App]. No. 688,915

Filed Dec. 7, 1967 Patented Dec. 7, 1971 Assignee Pennwalt Corporation Philadelphia, Pa.

METHOD OF PREPARING ALKYL SULFONYL CHLORIDE 10 Claims, 1 Drawing Fig.

US. Cl 260/543 R ..C07c 143/70 Field of Search 260/543 REACTOR TURBULENT REACTION ZONE [56] References Cited UNITED STATES PATENTS 3,248,423 4/1966 Stratton 260/543 Primary E.taminerLewis Gotts Assistant Examiner-Edward Jay Gleiiman Attorneys-William M. Epes and Stanley Litz -\1 GASEOU5 HCI and C]; To SCRUBBER COLUMNS OgERFLOW CONDUIT ALKYL SULFONYL CHLORIDE i.e., RSO CI, WHERE R IS ALKYL COOLING JACKET 7 SETTLING RESERVOIR ALKYL MERCAPTAN HAVING 5 w 20 CARBON ATOMS 1i COOLING L COIL T FRESH WATER or AQUEOUS HCI AQUEOUS HCL (CONTAINING SOME I3 DISSOLVED RSO CII o DIALKYL DISULFIDE RECYCLE CONDUIT 9 CHLORINE PRODUCT SEPARATION ZONE ALKYL SULFONYL CHLORIDE ite.,

RSO CI, WHERE R IS ALKYL HAVING 1 1'0 4 CARBON ATOMS METHOD OF PREPARING ALKYL SULFONYL CHLORIDE This invention relates to an improved process for preparing alkyl sulfonyl chlorides. More particularly, this invention concerns a continuous method of preparing an alkyl sulfonyl chloride which comprises reacting chlorine, water, and an alkyl mercaptan or alkyl disulfide, in aqueous hydrochloric acid medium in a turbulent reaction zone which is contiguous to product separation zone from which the alkyl sulfonyl chloride product is withdrawn.

In US. Pat. No. 2,277,325, R. Heuter et al. disclose a batch method of preparing an alkyl sulfonyl chloride wherein an alkyl mercaptan or dialkyl disulfide is suspended in water or a mixture of alcohol and water, and then treated with chlorine while stirring thoroughly. Two to 400 percent excesses of chlorine are used in carrying out the reaction. The reaction period in this batch process is of the order of L hours. Moreover, the reaction technique and product recovery steps are cumbersome and time consuming for this described process. In US. Pat. No. 3,248,423, G. B. Stratton prepares an alkyl sulfonyl chloride by reacting, batchwise, in a stirred aqueous medium, an alkyl mercaptan of four to 20 carbon atoms with chlorine together with a small amount of air or other source of oxygen. The mechanical agitation is necessary to keep the slurry in suspension. The disadvantages of the above-described batch process are the necessity for mechanical agitation and long reaction periods of the order of 1.5 to l2 hours.

The present invention involves a continuous method of preparing analkyl sulfonyl chloride having one to 20 carbon atoms of high purity and in high yield which comprises the steps of:

l. contacting an alkyl mercaptan or dialkyl disulfide having one to 20 carbon atoms in an alkyl group, preferably one to 12 carbon atoms, with at least about a stoichiometric amount of gaseous chlorine in a medium comprising aqueous concentrated hydrochloric acid solution in a reaction zone at a feed rate of from about 0.005 pound-mole to about one pound mole per hour of mercaptan or disulfide per cubic foot of reaction zone volume, at a temperature within the range of about l0 to about 50 C., preferably l0 to 35 C., whereby the reaction results in a vigorous evolution of gaseous HCl which causes turbulence in said reaction zone;

2. passing the reaction medium from the turbulent reaction zone into a product separation zone whereinthe alkyl sulfonyl chloride separates from the aqueous hydrochloric acid medi 3. recycling the aqueous hydrochloric acid medium to the turbulent reaction zone; and

4. withdrawing alkyl sulfonyl chloride from the product separation zone.

The mercaptan and disulfide reactants employed in the process of this invention can be represented by the formula RSX where X is hydrogen or a radical of the formula SR and where R and R are alkyl groups having one to 20 carbon atoms, preferably up to l2 carbon atoms. R and R' can be the same or different radicals. The alkyl groups can be substituted alkyl radicals having such substituent atoms and groups as hydroxyl, chlorine, bromine, fluorine, NH SO H, SO,Cl, and 80 R. The preferred reactants are methyl mercaptan and dimethyl disulfide, however, good yields and high quality product are also obtained with ethyl mercaptan, the propyl mercaptans, the butyl mercaptans, the amyl mercaptans, the hexyl mercaptans, heptyl mercaptans, octyl mercaptans, nonyl mercaptan, decyl mercaptan, undecyl mercaptan, dodecyl mercaptan, diethyl disulfide, dibutyl disulfide, dioctyl disultide, and the like.

The reaction embodied in the process of this invention can be exemplified by the following equation when using a mercaptan feed material:

RSH 3C1, 2Hg0 BS0 01 51161 concentrated aqueous H01 medium ill and when using a disulfide feed material:

RSSR 501, 411,0 ZRSO Cl 8H0! concentrated aqueous HCl medium or RSSR 501, 4H 0 RSO CI R'S0,C1+8HC1 concentrated aqueous H01 medium needed; the high turbulence required to provide the intimate contact of the reactants in the aqueous hydrochloric acid medium is produced by the evolution of the gaseous HCl byproduct. The amount of product which can be prepared per unit volume of reactor area is quite large and moreover, the yield of the alkyl sulfonyl chloride is remarkably good, i.e., at least percent and often at least percent, based on the mercaptan or disulfide feed. In addition, the size of reactor equipment required for high production is minimal because the required reaction time in the present process, i.e., holdup time of nonvolatile components in the reaction system, can advantageously be relatively very short, e.g., from less than one minute up to about 15 minutes, generally less than 5 minutes. This results in an appreciable savings in capital equipment expenditures. Thealkyl sulfonyl chloride product as recovered from the separation zone is of surprisingly high purity, generally requiring very little further processing, for example, topping" under reduced pressure to remove a small amount of. volatile impurities. This is conveniently accomplished by subjecting the product to a slight vacuum and somewhat elevated temperatures, for instance, 75 C. at mm. Hg. abs, to volatilize dissolved HC] and a small amount of residual moisture.

The method of the invention is clarified by referring to the attached drawing in which a diagrammatic flow sheet depicting a specific embodiment of the process is shown. The reactor system comprises the cylindrical reactor 16 and cylindrical settling reservoir 17 connected by overflow conduit 7 and recycle conduit 8. The reactor has optional cooling jacket 2 and the settling reservoir has an internal, coiled-tube heat exchanger 11 to remove the heat generated by the reaction and to control the temperature of the system within the desired limits. One or both of said heat exchangers can be replaced by heat exchangers situated in one or both of the conduits 7 and 8. The system is filled with concentrated aqueous hydrochloric acid solution and gaseous chlorine is metered from feed tank 5 through line 6 and sparged into the aqueous medium at the bottom of the reactor 16. Simultaneously, alkyl mercaptan or dialkyl disulfide or mixtures thereof is metered from feed tank 3 through line 4 into the reactor 16 at a point somewhat above the feed point of the chlorine. When feeding a higher dialkyl disulfide having a comparatively high melting point above about 50 50 it is advantageous to feed said compound as a solution in an inert solvent such as acetic acid, carbon tetrachloride, chloroform and chlorinated lower aliphatic hydrocarbons.

The intensity and vigor of the reaction causes much turbulence in the reaction zone 1 which results in the liquid level therein rising appreciably above the level of the overflow conduit 7. Byproduct gaseous HCl and unreacted chlorine pass from the reactor through line 9 to a demister unit and waterscrubber and aqueous caustic-scrubber columns. After the aqueous HCl reaction medium becomes saturated with alkyl sulfonyl chloride product, said product commences to separate therefrom in the product separation zone 10 and is continuously, or intermittently, withdrawn through line 14 or line 15, in the former case when the alkyl sulfonyl chloride has from 1 to 4 carbon atoms and the specific gravity thereof is thus greater than the specific gravity of the concentrated aqueous HCI medium, and in the latter case when the alkyl sulfonyl chloride has from five to 20 carbon atoms and the specific gravity thereof is therefor less than that of the aqueous medium. This separation of the product and its decantation is facilitated by maintaining a sufficient differential of specific gravities between the aqueous medium and the alkyl sulfonyl chloride product layers by continuously, or intermittently, withdrawing a small portion of the aqueous reaction medium from the product separation zone through line 13 while continuously, or intermittently, adding fresh water or aqueous HCl solution via line 12 to maintain the specific gravity differential and the proper liquid level in the system. It is to be understood by one skilled in the art that many variations and modifications can be made in the foregoing exemplary embodiment of the process without departing from the scope of inventive concept, for example, with regard to the type and location of entrance points for reactant streams and exit points for discharge streams.

It is desirable to carry out the process of the invention under atmospheric or slightly subatrnospheric pressures in order to facilitate removal of gaseous byproducts from the reaction zone. The temperature of the reaction may range from about to 50 C. however, highest yields are obtained at about 10 to 35 C.

As stated earlier, the reaction embodied herein is initiated and carried out continuously in concentrated aqueous hydrochloric acid solution. The reaction can be initiated in pure water but there is a likelihood of a flash fire in the reactor until the HCl content of the aqueous medium is established.

As previously stated, feed rates of reactants must be of a sufficient magnitude to produce vigorous turbulence in the reaction zone to ensure intimate contact of the reactants and a high yield of product while dispensing with the need of mechanical means of agitation therein and its attendant capital investment and maintenance costs. A feed rate of at least about 0.005 pound-mole per hour of mercaptan or disulfide per cubic foot of reaction zone is desirable. A practical upper limit for this feed rate is in the range of about one pound-mole per hour of mercaptan or disulfide per cubic foot of reaction zone. The preferred range is about 0.005 to about 0.03 pound-mole per hour per cubic foot.

lt is desirable to periodically monitor the density of the aqueous hydrochloric acid medium in the settling reservoir to ensure that there is a specific density differential between this layer and the alkyl sulfonyl chloride product layer in order to maintain a separation of the two phases in the product separation zone. The density differential is maintained by withdrawing a small requisite amount of the aqueous medium and replacing the withdrawn amount in the system with fresh aqueous HCl solution of fresh water. The withdrawn aqueous concentrated HCl medium contains dissolved alkyl sulfonyl chloride in a minor amount equivalent to the saturation concentration at the system temperature, for example about 10 percent of methane sulfonyl chloride at 25 C. This product can be recovered in useful form by hydrolyzing the alkyl sulfonyl chloride to the corresponding sulfonic acid.

The following examples which are set forth to further illustrate the method of this invention should not be construed as limitative of the scope of the invention as described herein and defined by the claims.

EXAMPLE 1 The apparatus used comprised a vertical, tubular, 4-inch diameter glass reactor 100 inches long connected to a 4-inch product separation zone) contained a water-cooled. coiledtube heat exchanger. The liquid volume of the settling reservoir was 4.4 gallons.

The system was filled with 37 percent aqueous HCl up to the overflow conduit. Gaseous chlorine was metered into the bottom of the reactor. Vaporized methyl mercaptan was metered into the reactor about 18 inches above the chlorine feed entrance. The reaction was very vigorous, causing much turbulence in the reaction zone so that the turbulent reaction zone was about 54 to 74 inches long, equivalent to a volume of about 2.9 to 4 gallons. Unreacted chlorine and byproduct HCl passed from the top of the reactor through a demister unit, a water scrubber column, and an aqueous caustic scrubber column from which the system was vented to the atmosphere. The reactant feed rates are given in the operating data presented hereinbelow. After about 50 minutes of operation, the aqueous HCl solution became saturated with methane sulfonyl chloride (about 10 percent concentration at 25 C.) which liquid product continuously precipitated from solution and was withdrawn from the bottom of the settling reservoir. In order to maintain an adequate density differential in the settling zone to permit the decantation of the methane sulfonyl chloride, a small portion of the concentrated aqueous HCl solution was intermittently withdrawn from the settling reservoir and replenished by fresh water. The specific gravity of the aqueous HCl phase ranged from about 1.2 to about 1.3 at 25 C., compared to a specific gravity for the ethane sulfonyl chloride product layer of 1.475 to 1.480 at 25C.

The data for the run is tabulated in the following table:

Duration of Run 23 hrs. 22 minutes Reaction System temperature range 20 to 28 C. Temperature for of run 25 C. Circulation rate of aqueous HCl phase 14 gallons/minute Methyl Mercaptan Feed Rate 4.46 lbs/hr. Total Methyl Mercaptan Fed 104 pounds Chlorine Feed Rate 20.7 lbs/hr. Total Chlorine Fed 483.4 pounds Excess chlorine based on CH,SH fed 5% Total water consumed 80.7 lbs Excess water based on CH,SH fed 3% Methane sulfonyl chloride collected 235.6 pounds Methane sulfonyl chloride production rate 10.1 lbs/hr. Average reaction time 0.5 minute Yield of methane sulfonyl chloride based on 99% pure CH,SH fed 95.6% Purity of methane sulfonyl chloride determined by: 1) Vapor phase chromatography 99.9% (2) Acid/base saponification (3) Chloride saponification 100% EXAMPLE 2 The techniques described in example 1 were modified slightly by substituting butyl mercaptan, metered as a liquid into the reaction zone, for the methyl mercaptan reactant of the previous example. The butyl sulfonyl chloride product was withdrawn as the lower phase from the settling reservoir; its specific gravity ranged from 1.229 to 1.233 at 20 C. compared to a specific gravity of 1.205 to l.215 at 20 C. for the upper-phase, aqueous HCl layer. The yield of the butyl sulfonyl chloride averaged 94 percent based on the butyl mercaptan fed. The purity of the product was 98.1 percent by acidbase hydrolysis and 98.3 percent by chloride hydrolysis.

EXAMPLE 3 Employing the techniques described in the previous examples, dimethyl disulfide was reacted with a stoichiometric amount of chlorine in concentrated aqueous HCl medium at 19 to 28 C. The yield of methane sulfonyl chloride product was 99 percent.

EXAMPLE 4 The procedures of the preceding examples were repeated using sec-butyl mercaptan as starting material and a reaction temperature of 20-25 C. The yield of sec-butyl sulfonyl chloride was 95.6 percent.

EXAMPLE 5 The procedures of the preceding examples were repeated using cyclohexyl mercaptan as starting material. The yield of cyclohexyl sulfonyl chloride was 99 percent.

EXAMPLE 6 Employing the techniques described in the preceding examples, octyl sulfonyl chloride was prepared by reacting octyl mercaptan with chlorine in concentrated aqueous HCl medium with the difference that the octyl sulfonyl chloride, specific gravity range of l.090-l.100 at was recovered by decantation as the upper-phase from the settling zone; the specific gravity of the lower-phase, aqueous i-lCl layer ranged from 1.19 to l.30 at 20 C. The yield of the essentially 100 percent pure octyl sulfonyl chloride, after topping, was about 95 percent on the octyl mercaptan consumed.

EXAMPLE 7 The techniques described in example 6 were repeated using dodecyl mercaptan as the mercaptan reactant. The specific gravity of the dodecyl sulfonyl chloride, withdrawn as product by decantation from the upper portion of the settling reservoir, was 1.040 at 20 C., compared to 1.20 at 20 C. for the aqueous HCl lower phase. The yield, after topping, of the essentially 100 percent pure dodecyl sulfonyl chloride was 97.3 percent on the mercaptan fed.

lclaim:

l. A continuous method of preparing an alkyl sulfonyl chloride have one to 20 carbon atoms in the alkyl group which comprises contacting a sulfur-containing reactant having the formula RSX, where X is hydrogen or a radical of the formula SR and where R and R are alkyl radicals having one to 20 carbon atoms, with chlorine in an amount ranging from stoichiometric up to about 5 percent excess based on the amount of the RSX feed, in a medium comprising aqueous concentrated hydrochloric acid solution in a reaction zone at a feed rate of from about 0.005 pound-mole to about one pound-mole per hour of RSX per cubic foot of the reaction zone, at a temperature of from about l0 to about 50 C., whereby the reaction of the RSX with chlorine and water results in a vigorous evolution of gaseous HCl which produces turbulence and intimate contact of the reactants in said reaction zone, passing the reaction medium from the turbulent reaction zone into a product separation zone wherein the alkyl sulfonyl chloride phase separates from the aqueous hydrochloric acid phase, recycling the aqueous hydrochloric acid phase to the turbulent reaction zone, and withdrawing alkyl sulfonyl chloride product from the product separation zone, the withdrawal of said product being from the bottom of the product separation zone when the alkyl sulfonyl chloride has from one to four carbon atoms, and said withdrawal being from the top of the product separation zone when the alkyl sulfonyl chloride has from five to 20 carbon atoms.

2. The method according to claim ll wherein the temperature of the reaction is from about 10 to 35 C.

3. The method according to claim 2 wherein the feed rate of RSX is from about 0.005 pound-mole to about 0.03 poundmole per hour per cubic foot of reaction zone.

4. The method according to claim 1 wherein R and R are alkyl radicals having one to 12 carbon atoms.

5. The method of claim 1 wherein the sulfur containing reactant is methyl mercaptan.

6. The method of claim 1 wherein the sulfur containing reactant is butyl mercaptan.

7. The method of claim 1 wherein the sulfur containing reactant is dimethyl disultide.

8. The method of claim 1 wherein the sulfur containing reactant is dibutyl disulfide.

9. The method of claim 1 wherein the sulfur containing reactant is octyl mercaptan.

10. The method of claim 1 wherein the sulfur containing reactant is dodecyl mercaptan.

P0-1050 UNITED. STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 2 004 Dated February 25. 1972 Inventofls) Roland Maurice Guertln It is certified that error appears in the above-identified patent I and that said Letters Patent are hereby corrected as shown below:

' Column 2', line 62, "50 50" should read -50G.

Column 4, line 28, "ethane" should read --.methane Column 5, line 17, after "percent" insert -based Column 5, line 27, after "percent" insert based- Signed and sealed this 30th day of- May 1972.

(SEAL) Attest:

EDWARD I'-I.FLbJTCHER,JR. ROBERT GOTTSCHALK [attesting Officer Commissioner of Patents 

2. The method according to claim 1 wherein the temperature of the reaction is from about 10 to 35* C.
 3. The method according to claim 2 wherein the feed rate of RSX is from about 0.005 pound-mole to about 0.03 pound-mole per hour per cubic foot of reaction zone.
 4. The method according to claim 1 wherein R and R'' are alkyl radicals having one to twelve carbon atoms.
 5. The method of claim 1 wherein the sulfur containing reactant is methyl mercaptan.
 6. The method of claim 1 wherein the sulfur containing reactant is butyl mercaptan.
 7. The method of claim 1 wherein the sulfur containing reactant is dimethyl disulfide.
 8. The method of claim 1 wherein the sulfur containing reactant is dibutyl disulfide.
 9. The method of claim 1 wherein the sulfur containing reactant is octyl mercaptan.
 10. The method of claim 1 wherein the sulfur containing reactant is dodecyl mercaptan. 